HLA haplotype on outcomes in pediatric Hodgkin patients enrolled in the italian AIEOP-LH2004 trial

Introduction The human leukocyte antigen (HLA) class I and class II genes are highly polymorphic and proteins encoded by them play an important role in self/non-self immune recognition. The identification of causal variants that modulate the susceptibility to a large number of infections and disease is problematic due to linkage disequilibrium (LD) that extends both across multiple HLA genes and non HLA genes. In a previous study evaluating polymorphic sites 3ʹ Untranslated region (UTR) HLA-G and Hodgkin disease (HL) in pediatric patients, we found the positive association between +3027-A frequencies and progression/relapse. In order to investigate the relationship between 3ʹUTR HLA-G and negative treatment outcome, the extended HLA haplotypes were analyzed.

Methods DNA from 113 pediatric HL patients (27 with progression/relapse (P/R)) treated using the AIEOP LH-2004 protocol were typed for HLA-A, HLA-G, HLA-F and HLA-E. In addition, two probes located in 3ʹUTR HLA-F (rs1633096) and near the HLA-DRA region (rs6903608) were studied. For allele frequency and epitope analysis the SKDM HLA Tool beta was used. The results are shown as P-values and odd ratios (OR) in the text.

Results Our data showed the presence of a LD block within the HLA class I region. The haplotype was composed of HLA-A*11, HLA-G*01: 01: 03 with +3027-A and HLA-F*01: 01: 02 with an alternating presence of the two HLA-E alleles (E*0101 or E*10103). The comparison of HLA-A allele frequencies between patient P/R and HL showed an association between HLA-A*11 with progression/relapse. Moreover, the alignment of the amino acids (AA) composing the anchorage pocket of the epitope from the most represented HLA-A alleles showed a Tyrosine (Y) in position 9 in P/R patients ( Y9, P=0,002674, OR=5,443). The presence of AA Y9 was statistically linked to the condition of heterozygosity and to the female gender (P=0,0045, OR=6,28; P=0,006222, OR=15,923 respectively). In a preliminary analysis of the class II marker, the rs6903608 T/C an association of the C allele with HL was observed suggesting that the HLA haplotype block structure could be further determined.

Conclusion We demonstrated that the HLA haplotype HLA-A*11, HLA-G*01: 01: 03 with +3027-A and HLA-F*01: 01: 02 was associated with progression/relapse in pediatric HL patients treated with the AIEOP LH-2004 protocol especially in female gender, however larger prospective studies will be necessary to confirm this relationship.